Copolyester and polyester resin composition comprising said copolyester

ABSTRACT

The present invention relates to a polyethylene terephthalate based copolyester modified by aliphatic dicarboxylic acid containing not less than 9 carbon atoms and poly(tetramethylene oxide)glycol, and to a polyester resin composition comprising said copolyester. 
     Said polyester resin composition exhibits excellent toughness, impact strength and moldability without harming the inherent characteristics of polyethylene terephthlate.

This application is a divisison of application Ser. No. 053,156, filedMay 21, 1987 now U.S. Pat. No. 4,772,652.

BACKGROUND OF THE INVENTION

The present invention relates to a copolyester with improved physicalproperties, particularly excelling in toughness, which is suited formolding.

The invention further relates to a resin composition comprising saidcopolyester, which is excellent in toughness, impact resistance andother mechanical properties, and moldability characteristics such asinjection moldability.

Polyethylene terephthalate (hereinafter sometimes referred to briefly asPET) has been used in various applications. While this resin has theadvantage of having a high secondary transition point and high meltingpoint as compared with polybutylene terephthalate, which is also athermoplastic polyester, it also has the disadvantage that when fullycrystallized with its molecular chains a non-oriented state, it isbrittle and unless reinforced with a reinforcing material such as glassfiber, shaped articles manufactured by injection molding or extrusionmolding are not of practical value. To impart ductility of polyethyleneterephthalate, there is the method comprising the addition of a metallicion neutralisate of a copolymer of an α-olefin with an α,β-ethylenicallyunsaturated carboxylic acid (Japanese Patent Laid-open No. 52-84244) butthe melt viscosity of the composition is markedly increased in thismethod so that trouble is encountered particularly in injection molding.Furthermore, the composition containing such a copolymer exhibits ofdiscoloration on heating.

On the other hand, as a composition having sufficient toughness, a glassfiber-reinforced polybutylene terephthalate composition is known butthis composition has the disadvantage of a low heat distortiontemperature.

PET whether reinforced or not with glass fiber or other filler materialdoes not possess a sufficiently high impact resistance and the problemof breakage of shaped articles in secondary processing and duringtransport is frequently encountered.

The general method for improving the impact resistance of PET, whetherreinforced or not, comprises adding a certain elastomeric polymer to thePET.

For example, Japanese Patent Publication No. 45-26223 discloses acopolymer of an α-olefin with a saturated aliphatic monocarboxylic acidvinyl ester as an impact strength improving agent for polyester resin.Japanese Patent Publication No. 45-26224 describes a copolymer of anacrylic ester with a conjugated diene as an impact strength improvingagent for polyester resin. In Japanese Patent Publication No. 45-26225,there is disclosed an ionomer as an impact strength improving agent.However, shaped articles manufactured by the above-mentioned methods arestill not fully satisfactory in impact strength.

Several other methods are known for improving the impact strength ofunreinforced PET or reinforced PET. By way of example, Japanese PatentLaid-open No. 51-144452, No. 52-32045 and No. 53-117049 teach thetechnique of blending a polyester resin with a copolymer of an α-olefinwith an α,β-unsaturated carboxylic acid glycidyl ester. The technique ofusing an ethylene copolymer as a third component in addition to theabove-mentioned copolymer is disclosed in Japanese Patent Laid-open No.58-17148 and No. 58-17151, and the technique of using polyphenylenesulfide as an additive component is described in Japanese PatentLaid-open No. 57-92044.

However, even these techniques are not fully capable of assuringsufficient impact strength.

Of all the plastics, aromatic polycarbonate is known to be the resinhaving the greatest impact resistance, and there was an early attempt toblend PET with this resin for improving the impact resistance of PET(Japanese Patent Publication No. 36-14035). More recently, U.S. Pat. No.4,257,937, for instance, teaches the combination of a polyacrylate resinand an aromatic polycarbonate resin as an impact strength improvingagent for polyester resin. By this method, a fairly high impactresistance has been obtained. Japanese Patent Laid-open No. 59-161460shows that in improving the impact strength of PET with a polyacrylateresin and an aromatic polycarbonate resin, the concomitant use ofpoly(1,4-butylene terephthalate) results in a further remarkableimprovement in impact strength. However, even by this method, the impactstrength (Izod impact strength) of the product is simply approachingthat of a PBT/ polyacrylate/ aromatic polycarbonate resin compositionand does no exceed it.

The present inventors previously proposed the use of a PBT polyester ina predetermined proportion in combination with a PET polyester anddisclosed that by modifying the blend with a metal salt of a certaincarboxyl group-containing polymer, a shaped article with a very highimpact strength can be obtained.

However, since this composition is prepared by blending the PETpolyester with the PBT polyester at a high temperature,transesterification is liable to take place. Moreover, when moldingscraps are pulverized and the resulting pellets are added to the moldingmaterial for reuse of the raw material, the high impact strengthattainable with the virgin molding material cannot be obtained.Moreover, the composition has a further disadvantage in that the shapedarticle is either poor in surface gloss or not satisfactory in moldreleasability.

Further, the conventional composition prepared by adding an elastomericpolymer to a polyester resin showed a decrease in impact strength whenthe shaped article was exposed to a high temperature for a long time.

On the other hand, it is known that the impact strength of afiller-reinforced polyester resin can be improved by blending a verylarge amount of an elastomer therewith (e.g. Japanese Patent PublicationNo. 59-30742). However, the incorporation of such a large amount of theelastomer results in the deterioration of the inherent heat resistanceand mechanical strength of the polyester.

Japanese Patent Laid-open No. 53-102360 teaches that the addition of PBTto a filler-reinforced PET composition results in an improved resistanceto warping. However, this blending does not provide for an increasedimpact strength.

The present inventors previously showed that the use of a PBT typepolyester in a specified proportion in combination with a PET typepolyester and the modification of the blend with a specified amount of ametal salt of a carboxyl group-containing polymer results in a very highproduct impact strength, with a notched Izod impact strength valueexceeding 20 kg.cm/cm being sometimes obtained. However, since thiscomposition is prepared by blending a PET type polyester with a PBT typepolyester at a high temperature, transesterification takes place so thatthe heat resistance of the shaped article is poor. Moreover, asmentioned above, when molding scraps are pulverized and added to thevirgin molding material for reclamation and reuse of the scraps, thehigh impact resistance achieved with the virgin material cannot beobtained.

The conventional glass fiber-reinforced polyethylene terephthalatereferred to above has the disadvantage that its impact resistancedecreases on prolonged exposure to high temperature and thatsatisfactory surface gloss and mold releasability cannot be achievedunless the mold temperature is set at a comparatively high level.

SUMMARY OF THE INVENTION

It is a first object of the invention to provide a novel tough polyesterwhich has overcome the brittleness, a major disadvantage, ofpolyethylene terephthalate, and yet retaining the other excellentcharacterisitcs of polyethylene terephthalate, namely, high meltingpoint, high rigidity, chemical resistance, mechanical properties andelectrical characteristics.

It is a second ob]ect of the invention to provide a polyethyleneterephthalate resin composition, whether filler-reinforced or not, whichis able to give moldings with excellent surface gloss and good moldreleasability even at low mold temperature without losing theabove-mentioned beneficial properties of the polyester.

It is a third object of the invention to provide a polyester resincomposition which has been markedly improved in impact resistance and inthe decrease of impact resistance on prolonged exposure to hightemperature while retaining the other excellent characteristics of theconventional polyethylene terephthalate.

It is a fourth object of the invention to provide a tough glassfiber-reinforced polyester composition which has been improved inbrittleness without losing the excellent high heat distortiontemperature and high regidity of the conventional glass fiber-reinforcedpolyethylene terephthalate composition.

The present invention relates, in a first embodiment, to a moldablecopolyester consisting essentially of the structural units of thefollowing formulas (I) to (IV): ##STR1## wherein R is a divalent groupavailable on elimination of carboxyl groups from an aliphaticdicarboxylic acid containing not less than 9 carbon atoms, and n is aninteger equal to 8 through 84, wherein (I) is bound to (III) and/or(IV), (II) is bound to (III) and/or (IV), and the sum of moles of (I)and (II) is substantially equal to the sum of moles of (III) and (IV),and the proportion of (II) is 0.2 to 10 moles and that of the repeatingunit --CH₂ CH₂ CH₂ CH₂ O) of (IV) is 1 to 20 moles to each 100 moles of(I).

The present invention relates, in a second embodiment, to a polyesterresin composition comprising (A) 100 parts by weight of the copolyesteraccording to the first embodiment of the invention, (B) 0.05 to 20 partsby weight of a nucleating agent and (C) 0.1 to 10 parts by weight of apolyalkylene glycol of the general formula R₁ O--R₂ O)_(n) _(1')(wherein R₁ and R_(1') are H or C₁₋₁₀ alkyl, acyl or aroyl, R₂ is C₂₋₄alkylene, n is a number not less than 5), and (D) 0 to 140 parts byweight of a reinforcing filler.

The present invention relates, in a third embodiment, to a polyesterresin composition with improved impact resistance which comprises (A)100 parts by weight of said copolyester of the first embodiment of theinvention, (B) 3 to 100 parts by weight of a metal salt of a copolymerconsisting of an α-olefin, an α, β-unsaturated carboxylic acid andoptionally a third vinyl monomer, and, (C) 0 to 60 weight percent, basedon the total composition, of a reinforcing filler.

DETAILED DESCRIPTION OF THE INVENTION

In undertaking research for toughening polyethylene terephthalate toovercome its brittleness, the present inventors set the restriction thatsaid toughening should be accomplished without affecting the highmelting and high rigidity features of polyethylene terephthalate incomparison with polybutylene terephthalate which is a polyester havingrelatively high toughness. The most outstanding feature of thecopolyester according to the first embodiment of the invention residesin the very fact that toughness could be build into polyethyleneterephthalate without substantially sacrificing the high melting pointand high rigidity characteristics of the resin.

The present inventors attempted to impart ductility to polyethyleneterephthalate by copolymerizing it with various polyalkylene glycols.The results were unsatisfactory, although some effects were observedwith poly(tetramethylene oxide)glycol. Surprisingly, however, it wasfound that when polyethylene terephthalate was copolymerized withpoly(tetramethylene oxide)glycol and an aliphatic dicarboxylic acidcontaining not less than 9 carbon atoms or an ester derivative thereof,the inclusion of even a small proportion of such comonomers results in amarked improvement in elongation a break of substantially unorientedcrystalline polyethylene terephthalate. This finding provided the basisfor the first invention.

The factors responsible for the effect of addition of said aliphaticdicarboxylic acid containing not less than 9 carbon atoms remain yet tobe elucidated but the following assumption may be advanced. Thus,whereas the copolymerization of polyethylene terephthalate withpoly(tetramethylene oxide)glycol alone gives a polymerization reactionproduct with a coarse phase separation texture, the use of an aliphaticdicarboxylic acid containing not less than 9 carbon atoms gives acopolymer with a delicate particulate dispersed phase texture asobserved by transmission electron microscopy of osmic acid-stainedspecimens. The present inventors consider that this alternation in phaseseparation pattern is associated with the observed improvement inductility, that is the toughening effect.

The first embodiment of the invention will hereinafter be described infurther detail.

The unit (I) of the copolyester according to the first embodiment of theinvention is derived from terephthalic acid or an ester derivativethereof such as dimethyl terephthalate, diethyl terephthalate and so on.Within the range not detrimental to the effects of the invention, thisunit (I) may be partially substituted by a dicarboxylic acid unit otherthan terephthalic acid and its ester derivatives.

The copolyester according to-the first embodiment of the invention, (II)is a unit derived from an aliphatic dicarboxylic acid containing notless than 9 carbon atoms or an ester derivative thereof. With regard tothe number of carbon atoms of said aliphatic dicarboxylic acid, thenumber of carbon atoms in the backbone chain between the carboxylicgroups (not including the carbon atoms of the carboxyl groups) is notless than 7, and said backbone chain may have a branch chain or maypartially form a ring. In the ring-forming aliphatic dicarboxylic acid,the number of carbon atoms between carboxyl groups means the smallestone. As examples of such aliphatic dicarboxylic acid containing not lessthan 9 carbon atoms, there may be mentioned linear dicarboxylic acidssuch as azelaic acid, sebacic acid, decanedicarboxylic acid,dodecanedicarboxylic acid, tetradecanedicarboxylic acid,hexadecanedicarboxylic acid, eicosanedicarboxylic acid, etc., dimeracids, hydrogenated dimer acids and their ester derivatives. Thesealiphatic dicarboxylic acids and ester derivatives can be used singly orin combination. The dicarboxylic acids particularly preferred for thepurposes of the invention are dimer acids and hydrogenated dimer acids.

The dimer acids used in the invention are prepared from unsaturatedfatty acids containing 18 carbon atoms, such as linolic acid andlinolenic acid, or monohydric alcohol esters thereof and consist mainlyof dimer acids containing 36 carbon atoms, although they contain minoramounts of monobasic acids and trimer acids. In order to accomplish theobjects of the invention, it is preferable to use diamer acids lean inmonobasic and trimer acids.

In the copolyester according to the first embodiment of the invention,the unit (II) is contained in a proportion of 0.2 to 10 moles,preferably not more than 5 moles, and for still better results, not morethan 3 moles per 100 moles of unit (I). In the above range, thecrystallized copolyester shows excellent ductility without a loss ofhigh rigidity, with consequent high toughness. When the proportion isless than 0.2 moles, toughness is not improved as in the case withpoly(tetramethylene oxide)glycol alone. When the proportion exceeds 10moles, the melting point of the crystallized product is depressed toomuch and the rigidity is also sacrificed so that the objects of thefirst invention are not accomplished.

In the first embodiment of the invention, the modification by theabove-mentioned proportion of unit (II) results in a remarkableimprovement in the brittleness of the crystallized polyethyleneterephthalate which is somewhat improved on modification withpoly(tetramethylene oxide)glycol alone. This effect cannot be achievedwith an aliphatic dicarboxylic acid containing less than 9 carbon atoms.There is virtually no upper limit to the number of carbon atoms of saidaliphatic dicarboxylic acid.

The unit (III) of the copolyester according to the first embodiment ofthe invention is the unit derived from ethylene glycol.

The unit (IV) of the copolyester according to the first embodiment ofthe invention is the unit derived from poly(tetramethylene oxide)glycol.The use of poly(tetramethylene oxide)glycol as a comonomer is essentialto the improvement in brittleness of substantially unorientedcrystalline polyethylene terephthalate and it is preferable that theresulting copolymer contains 1 to 20 moles of the repeating unit --CH₂CH₂ CH₂ CH₂ -O) of poly(tetramethylene oxide)glycol per 100 moles of theterephthalic acid unit. When the proportion is less than 1 mole, it isnot sufficient to attain an improvement in the brittleness ofpolyethylene terephthalate. When the proportion exceeds 20 moles, therigidity and melting point of the crystalline product are depressed sothat the objects of the invention cannot be accomplished. The proportionof this repeating unit is more preferably 3 to 15 moles and, for stillbetter results, not more than 10 moles.

The molecular weight o poly(tetramethylene oxide)glycol must be in therange of about 600 to 6000 (degree of polymerization (n): 8-84). The useof poly(tetramethylene oxide)glycol having a molecular weight not withinthe above range is undesirable, for it will reduce the ductility of thecomposition. The more preferable range of molecular weight is about 600to 2000 (degree of polymerization (n): 2 to 28).

In U.S. Pat. No. 4,211,678, poly(ethylene oxide)glycol is used in lieuof poly(tetramethylene oxide)glycol and this is copolymerized withterephthalic acid, ethylene glycol and dimer acids. However,copolyesters containing poly(ethylene oxide)glycol are poor inelongation at break and do not have the degree of toughness which isprovided by the present invention.

In the production of the polyethylene terephthalate copolymer accordingto the first embodiment of the invention, there may be incorporated,within the range not detrimental to the effects of the invention, asmall amount of additional monomers, for example polyfunctional monomerssuch as triols and tetraols, e.g. glycerol, trimethylolpropane,pentaerythritol, hexane triol 1,2,6, trimethylolethane, etc.,benzenetricarboxylic acids such as trimellitic acid, trimesic acid,pyromellitic acid, etc., benzenetetracarboxylic acids,polyhydroxycarboxylic acids containing 3 to 4 hydroxyl groups andcarboxylic groups and monofunctional monomers such as aliphaticmonocarboxylic acids, e.g. stearic acid, oleic acid, etc. and aromaticmonocarboxylic acids, e.g. benzoic acid, phenylacetic acid,diphenylacetic acid, 8-naphthoic acid and so on.

The copolyester according to the first embodiment of the invention canbe produced by the conventional method which is generally used in theproduction of polyesters. Generally, the polyethylene terephthalatecopolymer is produced by heating a mixture of reactants in the presenceor absence of a catalyst at atmospheric or superatmospheric pressure inan inert gaseous atmosphere. The reaction temperature is in the range of200° C. to 270° C. and, preferably, in the range of 230° C. to 260° C.After completion of the reaction, the resulting oligomer is subjected topolycondensation. This polycondensation reaction is carried out in thepresence of a known catalyst such as antimony, titanium, iron, zinc,cobalt, lead, manganese and germanium catalysts at a pressure of 15 mmHgor less, preferably not more than 1 mmHg, in the temperature range ofabout 270° C. to about 300° C.

The poly(tetramethylene oxide)glycol and said aliphatic dicarboxylicacid containing not less than 9 carbon atoms or ester derivative thereofcan be added before or during the transesterification or esterificationreaction but they are preferably added after the transesterification oresterification reaction, that is to say in the condensation stage.

The intrinsic viscosity of the copolyester according to the firstembodiment of the invention as determined in a 50:50 (w/w) mixture ofphenol and tetrachloroethane at 30° C. is in the range of about 0.5 toabout 1.5 and, preferably, in the range of about 0.5 to about 1.0.

The ¹ H-NMR spectrum (500 MHz) of the copolyester according to the firstembodiment of the invention shows a peak due to ethylene glycol attachedto the aliphatic dicarboxylic acid aside from the peak of ethyleneglycol attached to terephthalic acid and a peak not observed withpoly(tetramethylene oxide)glycol because of the formation of ester bondsat the terminal hydroxyl groups of poly(tetramethylene oxide)glycol,indicating that both the aliphatic dicarboxylic acid andpoly(tetramethylene oxide)glycol have been linked to the polymer chainby ester linkages to form an ethylene terephthalate copolymer. Thiscopolyester according to the first embodiment of the invention hasexcellent toughness in addition to the high melting point and highrigidity features of polyethylene terephthalate as such and is suitablefor use as a raw material for film, sheet and other shaped articles.

The copolyester of the first embodiment of the invention which possessthe above-mentioned high toughness plus the high melting point and highrigidity features of polyethylene terephthalate can be furtherformulated with other components to give resin compositions possessingvery desirable performance characteristics as described hereinafter.

The second embodiment of the invention is predicated on the finding thatthe addition of a nucleating agent and a polyalkylene glycol compound tothe copolyester of the first invention gives a polyester resincomposition which undergoes sufficient crystallization even at a lowmold temperature not more than 100° C. Furthermore, the resultingpolyester resin composition can be blended with a reinforcing fillersuch as glass fiber to give a reinforced polyester resin compositionhaving superior heat resistance and rigidity. Generally, theincorporation of a reinforcing filler results in a marked decrease intoughness in terms of tensile elongation, etc. as compared with theunreinforced composition. However, even at the usual incorporation levelof 30 to 40 weight percent of the reinforcing filler, the polyesterresin composition according to the second embodiment of the inventionwas found to exhibit excellent toughness as compared with theconventional filler-reinforced polyester resin composition.

The copolyester of the first invention can be used as copolyester (A)used in the second embodiment of the invention.

The nucleating agent (B) used in the second embodiment of the inventionmay be selected from among the materials which are generally used asnucleating agents for polyethylene terephthalate copolyesters. Forexample, inorganic nucleating agents such as neutral clay, e.g. talc,oxides, sulfates or silicates of Group II metals such as zinc oxide,magnesium oxide, calcium silicate, magnesium silicate, calcium sulfate,barium sulfate, etc., and organic nucleating agents such as monovalentor divalent metal salts of organic carboxylic acids containing 7 to 54carbon atoms or carboxyl group-containing polymers may be mentioned.

The research conducted by the present inventors has revealed that by asynergistic effect of polyalkylene glycol, the use of an organicnuleating agent gives a composition having high toughness and assuring amarkedly improved molded surface. As exemplary species of said organicnucleating agents, there may be mentioned Group Ia or Group IIa metalsalts of organic carboxylic acids containing 7 to 54, preferably 7 to25, carbon atoms, such as sodium stearate, calcium stearate, sodiumpelargonate, sodium behenate, sodium benzoate, calcium benzoate, sodiumterephthalate, lithium terephthalate, etc., and Group Ia or Group IIametal salts of copolymers of α-olefins of 2 to 5 carbon atoms, such asethylene, propylene, etc., with α, β-unsaturated carboxylic acids suchas acrylic acids, methacrylic acids and the like or copolymers ofaromatic olefins with α, β-unsaturated carboxylic acids, such asstyrene-maleic anhydride copolymer and the like. Examples of said GroupIa or Group IIa metals include sodium, potassium, lithium, calcium andthe like. Of the above-mentioned nucleating agents, the sodium orpotassium salts of carboxyl group-containing polymers are preferred inthe sense that the viscosity drop of the polyester is small at molding.In the above-mentioned copolymers, α-olefins or aromatic olefinspreferably account for 50 to 98 weight percent and more preferably 80 to98 weight percent. Particularly preferred is the sodium salt ofethylene-methacrylic acid copolymer. This copolymer characteristicallygives a composition assuring a very high degree of toughness.

Referring to the above-mentioned carboxyl group-containing polymers, itis not necessary that all the available carboxyl groups have beenneutralized. The preferred degree of neutralization is 40% or more andmore preferably 60% or more.

The proportion of said nucleating agent (B) is 0.05 to 20 parts byweight and preferably 0.1 to 10 parts by weight per 100 parts by weightof polyester resin (A). When the proportion exceeds 20 parts by weight,the mechanical properties of the moldings are sacrificed. When,conversely, the proportion is less than 0.05 part by weight, themoldabilty is not improved as much as desired.

As examples of the polyalkylene glycol (C) of the general formula:

    R.sub.1 O--R.sub.2 O).sub.n R.sub.1'

wherein R₁ and R_(1') each is a hydrogen atom or a C₁₋₁₀ alkyl, acyl oraroyl group; R₂ is a C₂₋₄ alkylene group; and n is a number not lessthan 5, which is used in the second embodiment of the invention, theremay be mentioned polyethylene glycol, polypropylene glycol,polytetramethylene glycol, etc., their mono- or dialkyl ethers (forexample, monomethyl or dimethyl ethers, monoethyl or diethyl ethers,monopropyl or dipropyl ethers and monobutyl or dibutyl ethers), mono- ordialkylates and mono- or diarylates (for example, monoacetylate,diacetylate, mono-2-ethylhexanoate, di-2-ethylhexanoate, monobenzoate,dibenzoate, etc.). In the second embodiment of the invention, it ispreferable to use a polyalkylene glycol forming alkyl ethers at bothends in that the intrinsic viscosity of the polyester resin is then notdecreased much at molding. The use of monoalkyl ethers or polyalkyleneglycols having free hydroxyl groups at both ends results in asubstantial reduction in intrinsic viscosity of the polyester resins atmolding and to avoid this result, it becomes necessary to use apolyester resin having a higher degree of polymerization. The degree ofpolymerization (n) of said polyalkylene glycol (C) must not be less than5. When n is less than 5, the polyalkylene glycol (C) tends to bleed onthe surface of the molding. The proportion of polyalkylene glycol (C) is0.1 to 10 parts by weight and, preferably, 1 to 5 parts by weight per100 parts by weight of copolyester (A). When the proportion exceeds 10parts by weight, the rigidity of the molding is sacrificed. If theproportion is less than 0.1 part by weight, the moldability is notimproved as much as desired.

The resin composition according to the second embodiment of theinvention can be formulated with a reinforcing filler (D) and theresulting reinforced composition offers various excellent properties.

The reinforcing fillers which can be used may be fibrous, sheet-like orgranular or of a mixed type. As examples of fibrous fillers, there maybe mentioned inorganic fibers such as glass fiber, carbon fiber,graphite fiber, metal fiber, silicon carbide fiber, asbestos fiber,wallastonite fiber, potassium titanate fiber, etc., whiskers, andvarious organic fibers. There is virtually no limitation on the type offiber that can be used but a suitable one is selected in accordance withthe desired object, such as improvement in mechanical properties, heatresistance, electrical conductivity, frictional characteristics, flameretardation and so on.

As examples of said sheet-like or granular fillers, there may bementioned mica (muscovite, phlogopite, etc.), sericite,clays, sheetglass(glass flake), glass bead, talc, metal foil and so on.

The addition of sheet-like materials alone is effective againstdeformation but in order to assure high mechanical strength and gooddimensional stability with little curling, they can be moreadvantageously used in combination with fibrous fillers.

While these fibrous, sheet-like and granular reinforcing fillers can beused singly or in combination, it is preferable to use at least afibrous filler as an essential component.

In the practice of the second embodiment of the invention, use of glassfiber is advantageous. This glass fiber may be an ordinary glass fiberwhich is commonly used for reinforcement of plastics and while itsdiameter is not critical, it is preferably in the range of 3 to 30 μ.Depending on the production process, various forms such as rovings andchopped strands can be employed. Moreover, the glass fiber is preferablysubjected to silanation, chrome-treatment or the like for improvedadhesion to the plastic material.

The proportion of said reinforcing filler, such as glass fiber, isgenerally not more than 140 parts by weight per 100 parts by weight ofthe copolyester. Particularly when 5 parts by weight or more of glassfiber is incorporated in the resin composition of the second embodimentof the invention, the heat distortion temperature of the composition isincreased to a level as high as that of the ordinary glassfiber-reinforced polyester resin compositions.

Moreover, even when a large amount of glass fiber is incorporated, thecomposition of the second embodiment of the invention characteristicallyassures a very high degree of toughness as compared with theconventional glass fiber-reinforced polyester compositions. In order toobtain a composition which assures both a high degree of toughness and ahigh heat distortion temperature, glass fiber is used in a proportion of10 to 100 parts by weight per 100 parts by weight of the polyesterresin.

Since the composition according to the second embodiment of theinvention shows a high rate of crystallization even at a comparativelylow temperature, molding at a mold temperature of about 80°to 100° C.,which is commonly used for the molding of general-purpose thermoplasticresins, results in a shaped article well and uniformly crystallized upto the surface layer and having an excellent surface gloss with goodmold releasability even in a short in-mold residence time. Moreover, theresulting shaped article is not only excellent in dimensional stabilitywith a minimum of curling but also shows high heat resistance, superiormechanical properties and a particularly high flexural modulus ofelasticity.

In the third embodiment of the invention, a metal salt of anα-olefin-α,β-unsaturated carboxylic acid copolymer is added to thecopolyester of the first invention, whereby the impact resistance of theshaped article is remarkably increased. Moreover, even when this shapedarticle is pulverized, the resulting powder blended with the unmoldedraw material, and the mixture molded, there is surprisingly obtained ashaped article having a high impact strength comparable to that of ashaped article molded from the virgin material. It is also surprisingthat such shaped articles retain high impact strength even afterprolonged exposure to a high temperature, e.g. 150° C. Moreover, aninjection-molded product having a very satisfactory surface gloss can beobtained with good mold releasability even at a comparatively low moldtemperature for PET resin compositions. In addition, even when areinforcing filler is incorporated, the resulting product fully retainsthe inherent properties (such as heat resistance and mechanicalstrength) of the filler-reinforced polyethylene terephthalate resincomposition.

As the copolyester (A) in the third embodiment of the invention, thecopolyester of the first embodiment of the invention can be used as is.The high impact strength of the composition of the third embodiment ofthe invention is derived from the presence of the above copolyester inthe composition.

In accordance with the third embodiment of the invention, a metal saltof a copolymer of an α-olefin with an α, β-unsaturated carboxylic acidand, if necessary, further with a third vinyl monomer (this copolymer issometimes referred to as the ionomer) (B) is incorporated in the resincomposition As examples of the α-olefin unit of said ionomer, there maybe mentioned ethylene, propylene and the like. As examples of said α,β-unsaturated carboxylic acid, there may be mentioned acrylic acid,methacrylic acid, maleic acid, fumaric acid, itaconic acid and the like.The third vinyl monomer includes, among others, ethyl acrylate, vinylacetate and the like. The metal may be a mono- to trivalent metal and ispreferably sodium, potassium, calcium, zinc or aluminum.

It has been found that when an alkali metal such as sodium is selectedas said metal, not only is a remarkably high impact strength obtainedbut this high impact strength is retained even after prolonged exposureto high temperature. According to the results of investigations by thepresent inventors, such a characteristic phenomenon is observed onlywhen a very special type of copolyester such as the one described hereinis used as the copolyester (A).

When zinc is selected as the metal, a resin composition with a minimumof coloration is obtained and it has been confirmed that suchcomposition is not readily discolored even on prolonged exposure to hightemperature.

The above ionomer can be produced by copolymerizing an α-olefin with anα, β-unsaturated carboxylic acid and, if necessary, further with a thirdvinyl monomer as aforesaid and, then, substituting some or all of thecarboxylic acid with a metal salt. As an alternative production processfor the ionomer, one may graft-polymerize an α,β-unsaturated carboxylicacid to a polymer or copolymer consisting of α-olefin units andoptionally a third vinyl monomer and, then, carry out the substitutionwith a metal salt. As a further alternative, one may copolymerize anα-olefin with an α,β-unsaturated carboxylic ester and, if necessary,further with a third vinyl monomer, hydrolyze the carboxylic ester bondsand, then, carry out the substitution with a metal salt. Any of theionomers prepared by these methods can be used in the third embodimentof the invention. A particularly preferred ionomer is a metal salt of anethylene-acrylic acid or ethylene-methacrylic acid copolymer. Suchionomers can be readily obtained from many sources, e.g. Mitsui ChemicalCo. which supplies HI-MILAN.

In the above ionomer, the carboxylic acid unit (inclusive of the saltthereof) of the copolymer should account for 1 to 30 mole percent of thetotal copolymer. If the proportion is less than 1 mole percent, theimpact strength of the polyester resin is not improved as much asdesired When the proportion exceeds 30 mole percent, the ionomer cannotbe easily blended with the polyester in the molten state in a shortamount of time. The preferred proportion of the carboxylic acid unit inthe ionomer in the third invention is 2 to 10 mole percent. In the thirdembodiment of the invention, it is not necessary that all the carboxylgroups in the ionomer have been neutralized by metal ions but, it isessential that at least 20 percent of all the carboxyl groups have beenneutralized. When the degree of neutralization is less than 20 molepercent, the impact resistance of the polyester resin is notsufficiently improved. The preferred degree of neutralization is 40% ormore and, for still better results, 60% or more.

The degree of neutralization can be found by infrared absorptionspectrometry of the copolymer. Thus, it can be estimated from the ratioof the νC═0 absorption intensity of the carboxyl groups forming salts tothe νC═0 absorption intensity of unneutralized carboxyl groups.

The proportion of (B) is 3 to 100 parts by weight, preferably 5 to 50parts by weight and, for still better results, 20 to 50 parts by weightper 100 parts by weight of the copolyester. When the proportion is lessthan 3 parts by weight, the impact strength of the shaped article is notimproved as much as desired, while the use of more than 100 parts byweight results in poor mechanical properties of the shaped article.

In the third embodiment of the invention, a reinforcing filler (C) canbe incorporated as desired. This reinforcing filler may be the same asthe one used in the second embodiment of the invention. Particularlypreferred for the purposes of the third embodiment of the invention isglass fiber and this glass fiber may be one of those employed in thesecond embodiment of the invention.

The proportion of the reinforcing filler is 0 to 60 weight percent,preferably 5 to 60 weight percent, and, more preferably, 10 to 50 weightpercent based on the total weight of the composition. When theproportion is low, the resulting composition does not have a sufficientmechanical strength required of any reinforced polyester. When theproportion exceeds 60 weight percent, the fluidity of the compositiondecreases thereby interfering with the molding procedure. When theproportion of reinforcing glass fiber is within the range of 20 to 45parts by weight, the composition according to the third embodiment ofthe invention has a particularly high impact strength, high heatdistortion temperature and rigidity and is excellent in fluidity so thatit is well balanced in properties.

The above-mentioned copolyester and ionomer are generally available inpowdery or particulate forms (pellets, chips, etc.). The desiredpolyester molding can be manufactured by mere mix-melting and molding ofthese materials together with the reinforcing filler. However, themixture can first be molded into pellets or chips and, then, thesepellets or chips can be melt-molded. Therefore, the mixture ofcopolyester, ionomer and reinforcing filler in the third embodiment ofthe invention means not only a mere mixture of the respective powders,particles and fillers but also a mixture of such components prepared bymix-melting.

The composition thus obtained provides shaped articles having a veryhigh impact strength which cannot be obtained from the conventional PETpolyester resins and, moreover, exhibiting only a minimum of decrease inimpact strength even on prolonged exposure to high temperature.Therefore, the invention contributes a great deal to the industry.

The above-mentioned copolyester and the composition comprising thecopolyester, which are provided by the present invention, may beformulated with various additives which are commonly used in polyestercompositions. For example, colors, mold releases, oxidation inhibitors,ultraviolet absorbers, flame retardants and so forth can be incorporatedas required. Moreover, within the range not interferring with theeffects of the invention, other resins such as other polyesters,polyolefins, acrylic resins, polycarbonates, polyamides, rubber-likeelastomers and the like can be blended.

Further, the present copolyester and composition can not only beinjection-molded but also molded by other techniques such as extrusioninto a variety of shaped articles. Shaped articles which can be obtainedby extrusion molding, include fibers, rods, films, sheets, plates, tubesand pipes, for instance. Moreover, by cutting such shaped articles,particulate or fragmentary molding materials such as chips and pelletscan be produced as desired. By injection molding, articles of desiredshapes can be manufactured according to the mold geometry employed.Whichever of these molding methods is employed, the resulting shapedarticles can be easily processed into final products by secondaryprocesses such as blow molding, drawing, vacuum molding and so on.

As uses for the copolyester and composition according to the presentinvention, there may be mentioned household utensils such as irons,hair-dryers, kitchenware, etc.; electrical and electronics parts such ascoil bobbins, switches, connectors, etc.; machine parts such as gears,covers, etc.; and automotive parts such as under-bonnet parts, shellsand so on.

The following examples are further illustrative of the presentinvention. Unless otherwise indicated, all parts are by weight.

EXAMPLE Run 1 Synthesis of copolyester A

An esterification reactor heated with a heat medium at 260° C. was fedwith a slurry composed of 1.5 kg (9.03 moles) of terephthalic acid, 0.67kg (10.8 moles) of ethylene glycol, 0.69 g of antimony trioxide, and0.13 g of phosphorous acid under pressure to carry out theesterification reaction. After the reaction mixture had become clear,the esterification was further continued until the carboxyl groupcontent of the reaction system was decreased to 600 μeq/g. This reactionmixture was fed under pressure to a polymerization reactor, where 43 gof poly(tetramethylene oxide)glycol with a molecular weight of about860, 43 g of dimeric acid (Versadyme 288, Henkel Japan) and 3.5 g ofIrganox 1010 (Ciba-Geigy) were added. The jacket temperature of thepolymerization reactor was increased to 280° C. and the internalpressure of the reactor was gradually decreased to 0.3 mmHg. Thepolymerization was conducted under these conditions for 60 minutes togive a copolyester. By means of a gear pump, the polymer was taken outin strand form from the nozzle, cooled with water and cut into pellets.The intrinsic viscosity of this polymer was 0.74 dl/g.

The above polymer was dissolved in hexafluoropropanol and analyzed by ¹H-NMR at 500 MHz. The analysis showed that it contained 1.13 moles ofdimer acid unit and 7.61 moles of poly(tetramethylene oxide)glycol unitper 100 moles of terephthalic acid unit.

By means of a hot press preheated to 280° C. the above copolyester wasmolded into a film with a thickness of about 50 μ and this film wasquenched with water to give a substantially amorphous quenched film.When its melting temperature (Tm) was determined from the peak crystalmelting temperature by DSC with a temperature incremental rate of 20°C./minutes. The Tm value was 249° C.

The copolyester pellets obtained as above were dried in vacuo at 120° C.for 12 hours. Then, the dried pellets were sandwiched betweenTeflon-coated iron plates with a 1 mm-thick spacer and were press-moldedat 280° C. The molding was immediately transferred to a separate hotpress pre-heated to 150° C., in which it was held for 5 minutes. Themolding was finally cooled to give a 1 mm-thick sheet which wassubstantially non-oriented and fully crystallized.

From the above sheet, a tensile testpiece was prepared using a preheatedNo. 2 dumbell punch for rubber use.

This testpiece was subjected to a tensile test using an Instronuniversal tester at the pulling speed of 0.5 cm/min. at 23° C. The meanfor 5 specimens (n=5) was calculated. The tensile characteristics of theproduct sheet are shown in Table 1.

Run 2

The esterification reaction between terephthalic acid and ethyleneglycol was conducted in the same manner as Run 1 and the reactionmixture was transferred to a polymerization reactor, where 43 g ofsebacic acid, 43 g of poly(tetramethylene oxide)glycol with a molecularweight of about 2000 and 3.5 g of Irganox 1010 (Ciba-Geigy) were added.Thereafter, the polycondensation reaction was conducted in the samemanner as Run 1 to give pellets of a copolyester. The intrinsicviscosity of the copolyester was 0.72 dl/g.

The composition analysis by H-NMR spectrometry showed that thiscopolyester contained 2.81 moles of sebacic acid unit and 7.48 moles ofpoly(tetramethylene oxide)glycol unit per 100 moles of terephthalicacid.

Runs 3 to 15

The esterification reaction between terephthalic acid and ethyleneglycol (butylene glycol in the case of copolyester N) at 260° C. Then,predetermined amounts of an aliphatic dicarboxylic acid and apoly(alkylene oxide)glycol were added and, by the same procedure as Run1, the various copolyesters shown in Table 1 were produced.

                                      TABLE 1                                     __________________________________________________________________________    Run No.    1   2    3   4   5    6   7   8   9                                Copolyester                                                                              A   B    C   D   E    F   G   H   I                                __________________________________________________________________________    Aliphatic dicarboxylic                                                                   Dimer                                                                             Sebacic                                                                            Dimer                                                                             Dimer                                                                             Azelaic                                                                            --  Dimer                                                                             Dimer                                                                             Adipic                           acid       acid                                                                              acid acid                                                                              acid                                                                              acid     acid                                                                              acid                                                                              acid                             Molecular weight of                                                                      about                                                                             about                                                                              about                                                                             about                                                                             about                                                                              about                                                                             --  about                                                                             about                            poly(tetramethylene                                                                      860 2,000                                                                              2,000                                                                             2,000                                                                             2,000                                                                              2,000   2,000                                                                             2,000                            oxide)glycol                                                                  Aliphatic dicarboxylic                                                                   1.1 2.8  0.23                                                                              1.1 3.0  --  0.89                                                                              4.0 3.1                              acid content of                                                               copolyester (moles per                                                        100 moles of tere-                                                            phthalic acid)                                                                Tetramethylene oxide                                                                     7.6 7.5  7.7 10.2                                                                              7.4  7.6 --  24.8                                                                              6.5                              repeating unit                                                                content of copolyester                                                        (moles per 100 moles                                                          of terephthalic acid)                                                         Intrinsic viscosity of                                                                   0.74                                                                              0.72 0.76                                                                              0.84                                                                              0.65 0.74                                                                              0.68                                                                              0.90                                                                              0.65                             copolyester (dl/g)                                                            __________________________________________________________________________    Run No.    10     11     12   13   14   15   16                               Copolyester                                                                              J      K      L    M    N*   O    P                                __________________________________________________________________________    Aliphatic dicarboxylic                                                                   octadecanedi-                                                                        octadecanedi-                                                                        Dimer                                                                              Dimer                                                                              Dimer                                                                              Dimer                                                                              Dimer                            acid       carboxylic                                                                           carboxylic                                                                           acid acid acid acid acid                                        acid   acid                                                        Molecular weight of                                                                      about  about  about                                                                              about                                                                              about                                                                              about                                                                              PEG*                             poly(tetramethylene                                                                      1,500  2,000  2,000                                                                              2,000                                                                              2,000                                                                              2,000                                                                              2,000                            oxide)glycol                                                                  Aliphatic dicarboxylic                                                                   1.4    1.7    2.3  6.1  0.84 12   1.1                              acid content of                                                               copolyester (moles per                                                        100 moles of tere-                                                            phthalic acid)                                                                Tetramethylene oxide                                                                     6.9    7.5    3.8  3.8  6.9  3.8  --                               repeating unit                                                                content of copolyester                                                        (moles per 100 moles                                                          of terephthalic acid)                                                         Intrinsic viscosity of                                                                   0.72   0.70   0.73 0.78 0.95 0.73 0.74                             copolyester (dl/g)                                                            __________________________________________________________________________     *Polybutyrene terephthalate polyester                                         *Poly(ethylene oxide)glycol                                              

Run 17

By the polymerization procedure described in Run 1, pure polyethyleneterephthalate with an intrinsic viscosity of 0.72 dl/g was prepared.

For each of the samples prepared in Runs 1 to 9, 11, 16 and 17, Tm wasdetermined by DSC and the tensile test was performed in the same manneras Run 1. The results are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                        Run  Tm     Young's modulus                                                                            Tensile strength                                                                         Elongation                                No.  (°C.)                                                                         (kg/cm.sup.2)                                                                              at break (kg/cm.sup.2)                                                                   at break (%)                              ______________________________________                                        1    249    17,000       650        110                                       2    247    13,000       480        78                                        3    251    16,000       680        95                                        4    247    10,000       580        130                                       5    247    13,000       480        53                                        6    251    18,000       510        22                                        7    253    17,000       450        16                                        8    237     7,500       380        200                                       9    244    13,000       500        25                                        11   249    15,000       520        95                                        16   248    14,000       510        32                                        17   254    17,000       700        10                                        ______________________________________                                    

Run 18 to 25

One-hundred parts by weight of a polyester mentioned in Table 3, 6 partsby weight of sodium salt of ethylene- methacrylic acid copolymer(HI-MILAN1707, Mitsui Polychemical), 3 parts by weight of polyethyleneglycol dimethyl ether (average molecular weight of polyethylene glycolmoiety 1,500) and 0.7 part by weight of Irganox 1010 (Ciba-Geigy) weredried and mixed and the mixture was charged into the hopper of a 40 mm(dia.) extruding machine (Osaka Seiki Kosakusha, Model 8 VSE- 40-28).The mixture was melted and extruded at a cylinder temperature of250°-270°-275°-275° C., the adapter temperature of 265° C. and a dietemperature of 265° C. and the resulting strand was cooled with waterand cut into pellets.

The pellets thus obtained were dried in a hot air current at 120° C. for15 hours and, then, molded into testpieces with an injection moldingmachine (Nikko-Ankerberg, Model V-15-75) at a cylinder temperature of240°-260°-275° C., a nozzle temperature of 280° C. and a moldtemperature of 90° C.

                                      TABLE 3                                     __________________________________________________________________________              Run No.                                                                                           23     24                                                 18  19  20  21  22  Polyethylene                                                                         Polyethylene                                                                         25                                Copolyester                                                                             A   B   C   F   G   terephthalate                                                                        terephthalate                                                                        P                                 __________________________________________________________________________    Tensile strength                                                                        470 460 460 455 470 540    450    450                               (kg/cm.sup.2)                                                                 Elongation at break                                                                     250 240 250  18  50  5     250     45                               (%)                                                                           Flexural strength                                                                       750 760 800 750 720 960    810    730                               (kg/cm.sup.2)                                                                 Flexural at strain                                                                      Not Not Not Not Not  10    Not    Not                               break (%) broken                                                                            broken                                                                            broken                                                                            broken                                                                            broken     broken broken                            Flexural modulus of                                                                     21,700                                                                            22,300                                                                            23,000                                                                            24,000                                                                            23,000                                                                            26,200 23,800 23,000                            elasticity- (kg/cm.sup.2)                                                     Heat distortion                                                                          70  68  71  72  73  78     61     72                               temperature (°C.)                                                      (18.6 kg/cm.sup.2)                                                            __________________________________________________________________________

The properties of the moldings are shown in Table 3. The compositionsaccording to the present invention invariably showed satisfactorymoldability and gave moldings with an excellent surface gloss. Moreover,the moldings obtained from the compositions of the invention showed veryhigh elongation values and, in the flexural test, showed large strainswithout being broken. Runs 26 to 37

One-hundred parts by weight of a copolyester mentioned in Table 4, 8parts by weight of sodium salt of ethylene- methacrylic acid copolymer(HI-MILAN Mitsui Polychemical), 3 parts by weight of polyethylene glycoldimethyl ether (average molecular weight of polyethylene glycol moiety1,000), 0.7 part by weight of Irganox 1010 and 48 parts by weight ofglass fiber (bundled chopped strand, 3 mm lengths, Nitto Boseki) werepremixed and the composition was charged into the hopper of a 40 mm(dia.) extruding machine (Osaka Seiki Kosakusha, Model 8 VSE-40-28). Thecomposition was melted and extruded at a cylinder temperature of250°-275°-275°-275° C., an adapter temperature of 265° C. and a dietemperature of 265° C. and the resulting strand was cooled with waterand cut into pellets. The kneading and extrusion could be effectedsmoothly and pellets in which the glass fiber were uniformly dispersedwere obtained.

The pellets thus obtained were dried in a hot air current of 120° C. for15 hours and testpieces were prepared from the dried pellets using aninjection molding machine (Nikko-Ankerberg, Model V-15-75) at a cylindertemperature of 240°-260°-280° C., a nozzle temperature of 280° C., and amold temperature of 90° C.

The properties of the moldings are shown in Table 4. The elongation atbreak was measured by the between-gages method under ASTM D 638. Thecompositions according to the present invention invariably showedexcellent moldability and gave moldings with a superior surface gloss.The compositions of the invention also showed high toughness, high heatdistortion temperatures and high rigidity. In contrast, the moldings inRuns 32 to 37 were either low in both elongation at break and bendingstrain with consequent poor toughness or low in tensile strength,flexural strength and heat distortion temperature although they showedfairly high toughness.

Run 38

The molding procedure of Run 26 was repeated except that the sodium saltof ethylene-methacrylic acid copolymer was used in a proportion of 0.04part by weight and the glass fiber in a proportion of 44.3 parts byweight.

The properties of the resulting moldings are shown in Table 4. Themoldings were inferior in surface smoothness and poor in dimensionalstability at annealing. It appeared that under the molding conditionsused, the polyethylene terephthalate was not sufficiently crystallized.Further, despite the small proportion of the sodium salt ofethylene-methacrylic acid copolymer which is low in elasticity, theproduct was lower than the product of Run 26 in both tensile strengthand flexural strength.

Run 39

The molding procedure of Run 26 was repeated except that thepolyethylene glycol dimethyl ether was used in a proportion of 11 partsby weight and the glass fiber in a proportion of 50.7 parts by weight.The properties of the resulting molded product are shown in Table 4. Thefluidity of the resin at molding was satisfactory and the surfacesmoothness of the product was also satisfactory. However, because of thehigh proportion of the plasticizer, the product was poor in toughness.Furthermore, bleeding of the plasticizer at annealing caused a loss ofsurface gloss.

Run 40

The molding procedure of Run 26 was repeated except that the glass fiberwas used in a proportion of 46.0 parts by weight and the polyethyleneglycol dimethyl ether was omitted. The molded product had a corrugatedsurface and since it was of no practical value, determination ofproperties was not performed.

Run 41

The procedure of Run 26 was repeated except that, in the manufacture ofpellets by extrusion, the glass fiber was used in a proportion of 44.4parts by weight and the sodium salt of ethylene-methacrylic acidcopolymer was replaced with 0.3 part by weight of sodium stearate, andtestpieces were prepared from the resulting pellets.

The properties of the testpieces are shown in Table 4. Each testpiecehad a satisfactory surface gloss and a high degree of toughness.

Run 42

The molding procedure of Run 26 was repeated except that the sodium saltof ethylene-methacrylic acid copolymer was used in a proportion of 3parts by weight and the glass fiber in a proportion of 45.6 parts byweight. The properties of the resulting molded product are shown inTable 4. Like the product of Run 26, the above product was excellent insurface smoothness and toughness.

Run 43

The procedure of Run 26 was repeated except that copolyester N was usedin lieu of copolyester A and the proportion of glass fiber was changedto 43.0 parts by weight.

The product had high toughness but showed a low heat distortiontemperature, failing to accomplish the objects of the present invention.

Run 44

A commercial polybutylene terephthalate resin (containing 30 weight % ofglass fiber) was dried by heating at 120° C. for 15 hours and testpieceswere prepared by means of an injection molding machine at a cylindertemperature of 235°-255°-255° C., a nozzle temperature of 255° C., and amold temperature of 60° C.

The properties of the resulting product are shown in Table 4. It isclear that the composition according to the present invention assuresthe toughness comparable to that of a polybutylene terephthalate resin.On the other hand, whereas the thermal deformation temperature ofpolybutylene terephthalate resin containing 30 weight % of glass fiberwas about 210° C, the composition according to the present invention(containing 30 weight % of glass fiber) showed a high value of 225° C.or higher.

                                      TABLE 4                                     __________________________________________________________________________    Run No.        26 27 28 29 30 31 32 33 34 35 36                               __________________________________________________________________________    Polyester      A  B  C  E  J  L  F  G  H  I  M                                (parts by weight)                                                                            100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                              Sodium salt of ethylene-                                                                     7  7  7  7  7  7  7  7  7  7  7                                methacrylic acid copolymer                                                    (parts by weight)                                                             Sodium stearate                                                                              -- -- -- -- -- -- -- -- -- -- --                               (parts by weight)                                                             Polyethylene glycol dimethyl                                                                 3  3  3  3  3  3  3  3  3  3  3                                ether (parts by weight)                                                       Irganox 1010   0.3                                                                              0.3                                                                              0.3                                                                              0.3                                                                              0.3                                                                              0.3                                                                              0.3                                                                              0.3                                                                              0.3                                                                              0.3                                                                              0.3                              (parts by weight)                                                             Glass fiber    48 48 48 48 48 48 48 48 48 48 48                               (parts by weight)                                                             Appearance of moldings                                                                       o  o  o  o  o  o  o  o  o  o  o                                Tensile strength                                                                             1,300                                                                            1,200                                                                            1,300                                                                            1,250                                                                            1,250                                                                            1,200                                                                            1,270                                                                            1,200                                                                            1,150                                                                            1,300                                                                            1,100                            (kg/cm.sup.2)                                                                 Elongation at break (%)                                                                      3.3                                                                              3.2                                                                              3.4                                                                              3.2                                                                              3.4                                                                              4.0                                                                              2.0                                                                              2.0                                                                              3.8                                                                              1.9                                                                              3.8                              Flexural strength                                                                            2,000                                                                            1,900                                                                            1,970                                                                            1,800                                                                            1,900                                                                            1,750                                                                            1,850                                                                            1,750                                                                            1,600                                                                            1,820                                                                            1,500                            (kg/cm.sup.2)                                                                 Flexural strain at break                                                                     3.5                                                                              3.6                                                                              3.5                                                                              3.3                                                                              3.5                                                                              4.2                                                                              2.1                                                                              2.1                                                                              3.5                                                                              2.2                                                                              3.6                              (%)                                                                           Flexural modulus of                                                                          9.0                                                                              7.8                                                                              8.2                                                                              7.3                                                                              9.0                                                                              7.0                                                                              8.7                                                                              8.8                                                                              6.5                                                                              7.5                                                                              7.8                              elasticy (10.sup.4 kg/cm.sup.2)                                               Izod impact strength                                                                         10.0                                                                             10.0                                                                             10.5                                                                             9.5                                                                              10.5                                                                             11.4                                                                             7.4                                                                              7.8                                                                              10.0                                                                             7.4                                                                              10.5                             (kg · cm/cm notched,                                                 1/8 inch thick)                                                               Heat distortion                                                                              228                                                                              226                                                                              230                                                                              226                                                                              230                                                                              225                                                                              230                                                                              233                                                                              210                                                                              222                                                                              200                              temperature (°C.)                                                      (load: 18.6 kg/cm.sup.2)                                                      __________________________________________________________________________    Run No.        37     38 39 40 41 42 43 44                                    __________________________________________________________________________    Polyester      Polyethylene                                                                         A  A  A  A  A  N  Polyethylene                          (parts by weight)                                                                            terephthalate                                                                        100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              terephthalate                                        100                      100                                   Sodium salt of ethylene-                                                                     7      0.04                                                                             7  7  -- 3  --                                       methacrylic acid copolymer                                                    (parts by weight)                                                             Sodium stearate                                                                              --     -- -- -- 0.3                                                                              -- --                                       (parts by weight)                                                             Polyethylene glycol dimethy                                                                  3      3  11 -- 3  3  --                                       ether (parts by weight)                                                       Irganox 1010   0.3    0.3                                                                              0.3                                                                              0.3                                                                              0.3                                                                              0.3                                                                              0.3                                      (parts by weight)                                                             Glass fiber    48     44.3                                                                             50.7                                                                             46.0                                                                             44.4                                                                             45.6                                                                             43.0                                                                             (30 weights %)                        (parts by weight)                                                             Appearance of moldings                                                                       o      x  o  x  o  o  o  o                                     Tensile strength                                                                             1,400  1,150                                                                            1,250 1,350                                                                            1,250                                                                            1,250                                                                            1,300                                 (kg/cm.sup.2)                                                                 Elongation at break (%)                                                                      1.8    2.2                                                                              1.9   1.9                                                                              3.4                                                                              3.4                                                                              3.3                                   Flexural strength                                                                            2,100  1,700                                                                            1,450 1,930                                                                            1,900                                                                            1,600                                                                            1,900                                 (kg/cm.sup.2)                                                                 Flexural strain at break                                                                     2.3    2.3                                                                              2.0   1.8                                                                              3.2                                                                              3.7                                                                              3.6                                   (%)                                                                           Flexural modulus of                                                                          10.4   8.3                                                                              6.2   9.3                                                                              8.5                                                                              7.5                                                                              9.0                                   elasticity (10.sup.4 kg/cm.sup.2)                                             Izod impact strength                                                                         7.4    7.5                                                                              7.4   9.5                                                                              10.0                                                                             9.5                                                                              9.0                                   (kg · cm/cm notched,                                                 1/8 inch thick)                                                               Heat distortion                                                                              235    228                                                                              210   227                                                                              228                                                                              206                                                                              210                                   temperature (°C.)                                                      (load: 18.6 kg/cm.sup.2)                                                      __________________________________________________________________________

Runs 45 to 54

One-hundred parts of each copolyester indicated in Table 5 and apredetermined amount of sodium salt of ethylene-methacrylic acidcopolymer (an ionomer, HIMILAN 1856, Mitsui Polychemical) werethoroughly dried in a hot air current and mixed with 1/10 of the amountof ionomer of Phosphite®168 (Ciba-Geigy) as an antioxidant. Theresulting composition was charged into the hopper of a 30 mm (dia.)two-axis extruding machine (Plastic Kogaku Kenkyusho) and melted andextruded at a cylinder temperature of 190°-270°-280°-285° C. (from thehopper side), the adapter temperature of 285° C. and the die temperatureof 275° C. to give a strand which was then cut into pellets.

The pellets thus obtained were dried at 120° C. for 12 hours and, then,preheated in a hot press with a 3 mm spacer at 280° C. for 5 minutesand, then, pressed at the pressure of 50 kg/cm² for 5 minutes. Thepressed product was further pressed with a press at 150° C. for 4minutes and, then, cooled in a cooling press for thoroughcrystallization to give a sheet with a thickness of about 3 mm.Testpieces were cut out from the sheet and the Izod impact strength(notched; ASTM D 256) was measured. The result is shown in Table 5.

The presence of at least 5 parts by weight of the ionomer assured a highimpact strength.

The compositions according to the invention as prepared by varying thesort, molecular weight and proportion of the aliphatic dicarboxylic acidand poly(tetramethylene oxide)glycol in the copolyester invariablyshowed high impact strength values. The moldings obtained were allowedto stand in an air bath at 150° C. for 7 days and their Izod impactstrengths were determined. The results are shown in Table 5.

Despite the prolonged exposure to a high temperature, the moldingsretained high impact strengths. Moreover, the moldings had satisfactorysurfaces.

Runs 55 to 62

Copolyesters were produced under various conditions, namely withoutaddition of an aliphatic dicarboxylic acid (copolyester F, Run 55),without addition of poly(tetramethylene oxide)glycol (copolyester G, Run56), addition of an excess thereof (copolyester H, run 57), addition ofan aliphatic dicarboxylic acid with a small carbon number (copolyesterI, Run 58) and addition of an excess of aliphatic dicarboxylic acid(copolyester O, Run 59), and each copolyester was molded in the samemanner as Run 48. Izod impact strength data on the products are shown inTable 5.

The incorporation of a ionomer invariably resulted in an improved impactstrength after molding but when the molded products were exposed to hightemperature for a long time, they showed a large variation in impactstrength probably due to local degradation, thus lacking in thestability of quality. It is thus clear that a stable and high impactstrength can be obtained only with compositions containing a copolyesterin which the sort and amount of aliphatic dicarboxylic acid and theamount of poly(tetramethylene oxide)glycol are each within the range ofthe present invention.

Run 60

The procedure of Run 48 was repeated except that a polyethyleneterephthalate with an intrinsic viscosity of 0.74 dl/g was used in lieuof the copolyester and the impact strength of the resulting product wasdetermined. The result is shown in Table 5.

In the case of unmodified polyethylene terephthalate, the incorporationof an ionomer results in some improvement in impact strength but amarked reduction in impact strength occurred when the product wasexposed to high temperature for a long time.

Run 61

A shaped article was manufactured in the same manner as Run 47 exceptthat a ethylene-ethyl acrylate copolymer (Yukalon X-190-1, MitsubishiPetrochemical) was used in lieu of the ionomer. The impact strength dataon the article are given in Table 5.

The mere use of a polymer not having formed a metal salt failed to givea high impact strength.

Run 62

The procedure of Run 48 was repeated except that poly(ethyleneoxide)glycol-modified polyester P was used as the copolyester. Theimpact strength of the shaped article showed a marked decrease when itwas exposed to high temperature for a long time.

Runs 63 to 65

Using an ethylene-methacrylic acid copolymer zinc salt (tradename,HI-MILAN 1855, Mitsui Polychemical) as the ionomer, shaped articleswere manufactured in the same manner as Runs 48, 50 and 51,respectively. These articles were white without a yellow cast. Impactstrength data on these shaped articles is shown in Table 6.

When allowed to remain in an air bath at 150° C. for 7 days, thearticles remained substantially uncolored.

                                      TABLE 5                                     __________________________________________________________________________                             Izod impact test, notched,                                                    kg · cm/cm                                                           Immediately                                                                          After 7 days                                                                         After 7 days                           Run No.                                                                            Copolyester                                                                          Ionomer   parts                                                                            after molding                                                                        at 70° C.                                                                     at 150° C.                      __________________________________________________________________________    45   A      HI-MILAN 1856*.sup.(1)                                                                   1 3      --     --                                     46   A      "         7.5                                                                              26     --     --                                     47   A      "         15 38     --     --                                     48   A      "         30 110    105    96                                     49   A      "         45 105    --     --                                     50   J      "         30 105    100    90                                     51   C      "         30 115    113    102                                    52   D      "         30 130    124    105                                    53   E      "         30 90      90    60                                     54   M      "         30 95      93    85                                     55   F      "         30 90     .sup.  1316-35*.sup.(3)                       56   G      "         30 85     17-42  12                                     57   H      "         30 95     20-60  15                                     58   I      "         30 83     15-30  10                                     59   O      "         30 93     24-70  17                                     60   Polyethylene                                                                         "         30 76      14    13                                          terephthalate                                                            61   A      Yukalon X-190-1*.sup.(2)                                                                30 15     --     --                                     62   P      HI-MILAN 1856.sup.                                                                      30 90     .sup.  1320-60*.sup.(3)                       __________________________________________________________________________     *.sup.(1) Sodium salt of ethylenemethacrylic acid copolymer (Mitsui           Polychemical)                                                                 *.sup.(2) Ethyleneethyl acrylate copolymer (Mitsubishi Petrochemical)         *.sup.(3) The range of values is shown because of a large variation of        data.                                                                    

Runs 66 to 69

Shaped articles were manufactured in the same manner as Run 63 exceptthat the kind of copolyester was changed The impact strength values ofthe shaped articles are given in Table 6. When such other kinds ofcopolyesters were used, the impact strength was high at the stageimmediately after molding but experienced a marked decrease on prolongedexposure to high temperature. In Run 69 in which polyethyleneterephthalate was used in lieu of the copolyester, the impact strengthwas very low even at the stage immediately after molding.

                                      TABLE 6                                     __________________________________________________________________________                            Izod impact test, notched,                                                    kg · cm/cm                                                           Immediately                                                                          After 7 days                                                                         After 7 days                            Run No.                                                                            Copolyester                                                                          Ionomer  parts                                                                            after molding                                                                        at 70° C.                                                                     at 150° C.                       __________________________________________________________________________    63   A      HI-MILAN 1855                                                                          30 127    110    32                                      64   J      "        30 94     88     25                                      65   C      "        30 105    95     27                                      66   F      "        30 92     13     --                                      67   G      "        30 100    18     --                                      68   I      "        30 97     12     --                                      69   Polyethylene                                                                         "        30 18     --     --                                           terephthalate                                                            __________________________________________________________________________

Runs 70 to 82

In the same manner as Run 45, the copolyester, ionomer and glass fiberwere blended as shown in Table 7 to prepare resin compositions. Usingthese compositions, testpieces were prepared and the impact strength ofeach testpiece was determined. The results are shown in Table 7.

When the proportion of the ionomer was not less than 5 parts by weight,high impact strength values were obtained.

The compositions according to the present invention invariably gavetestpieces showing high impact strength values. These testpieces wereallowed to rest in an air bath at 150° C. for 7 days and the Izod impactstrength of each testpiece was determined. The results are shown inTable 7. Despite the prolonged exposure to high temperature, thesetestpieces retained high impact strength values. The flexual strength ofeach testpiece was also determined in accordance with ASTM D 790. It wasfound that the products according to the present invention invariablyshowed high flexual strength values.

When the proportion of the ionomer was one part by weight outside of thescope of the invention, the impact strength of the resulting shapedarticle was inadequate (Run 70).

Runs 83 to 87

Shaped articles were manufactured in the same manner as Run 73 exceptunder the varied conditions, namely without addition of an aliphaticdicarboxylic acid (copolyester F), without addition ofpoly(tetramethylene oxide)glycol (copolyester G), with addition of anexcess of poly(tetramethylene oxide)glycol (copolyester H), withaddition of an aliphatic dicarboxylic acid with a small carbon number(copolyester I) and with addition of an excess of aliphatic dicarboxylicacid (copolyester 0). The Izod impact strength and flexual strength weredetermined. The results are shown in Table 7.

Comparison of Run 73 with Runs 83 to 87 shows that the latter productsare inferior to the products of Run 73 in both the impact strengthimmediately after molding and that after 7 days at 150° C. Particularlythe products of Run 85 to 87 are fairly low in flexual strength.

Run 88

A shaped article was manufactured in the same manner as Run 73 exceptthat a polyethylene terephthalate with an intrinsic viscosity of 0.74dl/g was used in lieu of the copolyester, and its impact strength wasdetermined. The result is shown in Table 7.

In the case of the unmodified polyethylene terephthalate, theincorporation of an ionomer failed to achieve an improvement in impactstrength.

Run 89

A shaped article was manufactured in the same manner as Run 73 exceptthat an ethylene-ethyl acrylate copolymer (Yukalon X-190-1, MitsubishiPetrochemical) was used in lieu of the ionomer, and its impact strengthwas determined. The results are shown in Table 7.

The use of a polymer not having formed a salt failed to achieve a highimpact strength.

                                      TABLE 7                                     __________________________________________________________________________                                   Izod impact test, notched,                                                    kg · cm/cm                                                                         Flexural                                                  Glass fiber,                                                                        Immediately                                                                          After 7 days                                                                         strength                         Run No.                                                                            Copolyester                                                                          Ionomer   parts                                                                            wt. % after molding                                                                        at 150° C.                                                                    kg/cm.sup.2                      __________________________________________________________________________    70   A      HI-MILAN 1856*.sup.(1)                                                                   1 30     5     --     1,80                             71   A      "         10 30    12     12     1,80                             72   A      "         20 30    15     14     1,80                             73   A      "         30 30    21     17     1,80                             74   A      "         30 20    15     --     1,55                             75   A      "         30 40    24     --     2,10                             76   A      "         30  3    12-33  --       40                             77   A      "         45 30    19     --     1,60                             78   J      "         30 30    18     17     1,70                             79   C      "         30 30    17     15     1,85                             80   D      "         30 30    22     18     1,75                             81   E      "         30 30    17     16     1,80                             82   M      "         30 30    20     17     1,70                             83   F      "         30 30    12     10     1,75                             84   G      "         30 30    11     10     1,70                             85   H      "         30 30    14     11     1,55                             86   I      "         30 30    12     11     1,65                             87   O      "         30 30    13     11     1,50                             88   Polyethylene                                                                         "         30 30    11     10     1,70                                  terephthalate                                                            89   A      Yukalon X-190-1*.sup.(2)                                                                30 30     9     --     1,70                             __________________________________________________________________________     *.sup.(1) Sodium salt of ethylenemethacrylic acid copolymer (Mitsui           Polychemical)                                                                 *.sup.(2) Ethylenemethyl acrylate copolymer (Mitsubishi Petrochemical)   

What is claimed is:
 1. A moldable copolyester consisting essentially ofstructural units of the following formulas (I) to (IV): ##STR2## whereinR is a divalent group available on elimination of carboxyl groups froman aliphatic dicarboxylic acid containing 18-54 carbon atoms, and n isan integer equal to 8 through 84, wherein (I) is bound to (III) and/or(IV), (II) is bound to (III) and/or (IV), and the sum of moles of (I)and (II) is substantially equal to the sum of moles of (III) and (IV),and unit (II) is contained in a proportion of from 0.2 to 10 moles per100 moles of unit (I) and the repeating unit --CH₂ CH₂ CH₂ CH₂ O)--of(IV) is contained in a proportion of from 1 to 20 moles per 100 moles ofunit (I).
 2. A copolyester according to claim 1 wherein (II) iscontained in a proportion of 0.2 to 5 moles to 100 moles of (I).
 3. Acopolyester according to claim 1 wherein the repeating unit --CH₂ CH₂CH₂ CH₂ O--of (IV) is present in a proportion of 3 to 15 moles to 100moles of (I).
 4. A copolyester according to claim 1 wherein R in thestructural unit of (II) is a divalent group available on elimination ofcarboxyl groups from at least one aliphatic dicarboxylic acid containing16 to 54 carbon atoms.
 5. A copolyester according to claim 4 wherein Rin the structural unit of (II) is a divalent groups available onelimination of carboxyl groups from at least one dicarboxylic acidselected from the group consisting of octadecanedicarboxylic acid, dimeracids and hydrogenated dimer acids.
 6. A copolyester according to claim4 wherein R in the structural unit of (II) is a divalent group availableon elimination of carboxyl groups from at least one dicarboxylic acidselected from the group consisting of dimer acids and hydrogenated dimeracids.
 7. A copolyester according to claim 1 which exhibits an intrinsicviscosity of 0.5 to 1.5.
 8. A shaped article fabricated from acopolyester according to claim 1.